Many petroleum oil refineries employ so-called desalters wherein crude oil mixed with water, which may or may not contain a number of chemicals, is treated in order to remove the water from the oil and to extract from the oil or oil emulsified with water (from the oil-producing formation) various salts and/or metal values or compounds contained therein. These metal compounds may include iron, vanadium and nickel compounds which can poison expensive FCCU (fluid catalytic cracking unit) catalysts used in cracking fractions or portions (usually distillates) of the oil.
Other oil refinery operations produce so-called slop oil emulsions which must be demulsified to remove water and/or contaminants before such oils can be further processed or blended for sale.
Other industrial operations, including steel mills and many chemical plants, produce water-in-oil emulsions which are difficult to break.
A number of methods and chemical compositions have been employed to break the foregoing type emulsions, with varying results. The emulsions either take too long a time to break, resulting in a `bottleneck` in the refinery or other industrial processes, or they do not break cleanly resulting in troublesome interfacial problems.
Some oil refineries have previously used high molecular weight polymers in petroleum oil desalting units but with poor results. For example, copolymers of polypropylene glycol and ethylene oxide have been used. (Pet. Products Handbook--Guthrie (McGraw-Hill Book Co., 1960).